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NNTP-Posting-Date: Tue, 25 Aug 2015 16:35:56 -0500
Newsgroups: alt.folklore.computers
Subject: Re: very basic tube questions--twin triode, "mu" rating; heptode
References: <9a606427-bd74-4c8a-9b0e-1874f3692261@googlegroups.com>
From: floyd@apaflo.com (Floyd L. Davidson)
Organization: __________
Date: Tue, 25 Aug 2015 13:35:50 -0800
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hancock4@bbs.cpcn.com wrote:
>In reading C&A, I found an ad by Sylvania with specs for
>various tubes.  Knowing extremely little tubes, could
>someone expand a little bit on the following...
>
>1) What is a "twin", as in the difference between a 5844
>triode and a 5965 _twin_ triode?  How would they be
>used?

That describes two units built into one envelope.

The 5844 is a twin triode with a 7 pin base, where both of the
triodes share a common cathode.  The specifications suggest it
would be useful for a DC switching function.

The 5965 is a twin triode with a 9 pin base, where the two
triode have separate cathodes.  It has a higher mu (gain), but
in several ways is similar to the above 5844.

>2) What does "mu" mean, as in 6211 Medium mu twin
>triode, and 5687 Low mu twin triad?  How would they be
>used?

Essentially mu is the gain.  It is the change in plate current
divided by the change in grid voltage that caused the change.
Higher values are useful for higher gain applications, while
lower values are useful for switching applications (or higher
output for power amplifiers).  Note also that higher gain would
usually mean shorter life and less stable operation.

Tubes varied significantly between manufacturers, between batches
off the same production line, and with age.  With circuits where
manual adjustment was not desired, it was not uncommon to stick with
one manufacturer, to "burn in" tubes for at least 48 hours, and then
to hand pick tubes within a given mu range.

-- 
Floyd L. Davidson                         http://www.apaflo.com/
Ukpeagvik (Barrow, Alaska)                      floyd@apaflo.com